Electronic control system for internal combustion engine injectors

ABSTRACT

An arrangement defining the duration of the electronically controlled injection periods in an internal combustion engine, by returning the flip-flop controlling the actuation of an injector into its prior condition putting an end to the operation of the injector. To this end, a uni-junction transistor is grounded through one base while the other base is subjected to a voltage varying in accordance with the operation of the engine and defining the actually desired duration of injection. This duration is thereby brought to an end by the discharge of a condenser fed by the flip-flop and connected with the emitter of the uni-junction transistor while an auxiliary transistor transmits the voltage of the discharged condenser to the flipflop to return the latter to its prior condition.

United States Patent Monpetit 51 June 13, 1972 Louis A. France Soclete des Procedes Modernes dlnjection Sopromi, Les Mureaux, France Feb. 6, 1970 Inventor:

[72] Monpetit, L'Etang-la-Vllle,

Assignee:

[30] Foreign Application Priority Data Feb. 12, 1969 France ..6903274 References Cited UNITED STATES PATENTS 3,521,606 7/1970 Schmidt ..123/32 EA 3,028,507 4/1962 Sacks ..307/288 3,456,628 7/1969 Bassot et aL. 3,497,725 2/1970 Lorditch, Jr ..307/273 5 Primary Examiner-Laurence M. Goodridge Attorney-Kenyon & Kenyon Reilly Carr & Chapin ABSTRACT An arrangement defining the duration of the electronically controlled injection periods in an internal combustion engine, by returning the flip-flop controlling the actuation of an injector into its prior condition putting an end to the operation of the injector. To this end, a uni-junction transistor is grounded through one base while the other base is subjected to a voltage varying in accordance with the operation of the engine and defining the actually desired duration of injection. This duration is thereby brought to an end by thedischarge of a condenser fed by the flip-flop and connected with the emitter of the uni-junction transistor while an auxiliary transistor transmits the voltage of the discharged condenser to the flip-flop to return the latter to its prior condition.

4 Claims, 2 Drawing V W W PATENTEDJUH 131912 sum 1 OF 2 INVENTOR LOUIS A. MONPE'IT 0 ORA/5V5 PATENTEnJun 13 I972 3.669.080

sum 2 OF 2 //V VEN 701-? LOU/S A MON ET/T ELECTRONIC CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE INJECTORS In a known arrangement as shown in U.S. Pat. No. 3,456,628 assigned to the assignee of this application, the beginning and end of the injection of fuel into an internal combustion engine are controlledby an electronic circuit including a flip-flop constituted by at least two semi-conductor elements of the transistor or thyristor type. The starting of the injection is then triggered by a pulse fed to the control electrode of one of said semi-conductor elements, which pulse is formed by generating means associated with the rotation of the engine, while the end of the injection is controlled by a second pulse produced by delay means provided with a plurality of independent inputs. Said delay means is constituted in this prior art by a uni-junction transistor theemitter of which is connected with a resistance and a condenser which latter is charged with a predetermined voltage through said resistance, whereas the two bases of said uni-junction transistor are supplied with a further voltage so that the'second pulse is triggered when the two voltages are equal, except for a welldefined proportionality factor.

According to said prior art, the duration of injection is adjusted by causing the time elapsed between the first actuating pulse starting the injection andthe second pulse stopping said injection to vary. This is obtained essentially by adjusting the resistance connected with the emitter of the uni-junction transistor while an auxiliary adjustment is obtained by modifying the voltage applied to the base No. 2 of said transistor.

However, if it is desired to modify the duration of injection by acting chiefly on the voltage applied to the base No. 2 of the uni-junction transistor, it is necessary to modify said voltage within a broadrange. In such a case one is obviously limited, on the one hand, by the generally low voltage providedfor the system, and, on the other hand, by the fact that the uni-junction transistor can be made conductive only if the voltage applied to -'the base No. 2 of said uni-junction transistor is lower than the voltage charging the condenser.

On the other hand, if very low voltages, are applied tothe base No. 2 of the uni-junction transistor, the energy of the pulse controlling the end of the injection is small and there is a risk of the bistable flip-flop, energized by the signal, starting the injection, without any possibility of the flip-flop returning to its former condition, the uni-junction transistor being stabilized under downstream current conditions.

The present invention has for its object to eliminate these drawbacks and more particularly it covers delay means cooperating with a bistable flip-flop associated with a unijunction transistor or an equivalent semi-conductor system, the base No. l'of which is grounded while its base No. 2 is fed with a variable voltage, the value of which is controlled by the operative parameters of the engine. The emitter of said unijunction transistor is connected through one or more resistances with the junction point connecting the resistance with the condenser charged through said resistance and the bistable flip-flop when the latter is in the ON state. Said bistable flip-flop switched to the OFF state by means of a transistor, the collector of which is connected with a suitable point of the bistable flip-flop while its emitter is connected with the emitter of the uni-junction transistor and its base is connected with said connecting point between the condenser and its charging resistance.

The invention may be further developed by connecting a diode between the bistable flip-flop and the resistance-andcondenser circuit in order to eliminate any modification in the duration of the injection produced by a modification in the frequency of operation. 7

According to a further feature of the invention, said diode is constituted by a constant current diode or by any other equivalent arrangement.

By way of example and in order to further the understanding of the following description, there is illustrated in the accompanying drawings an embodiment of a bistable flip-flop associated with delay means according to the invention, in which:' I

FIG. 1 is an overall diagram of the fuel injection system.

. bered 7-to 10.

The circuit has a pressure regulating discharge valve 6 and if necessary a mechanical or pneumatic back pressure accumulator 11.

The electrical and electronic circuitry is fed by a source of energy, generally the storage battery 13, which itself is connected in a conventional manner to a generator 14 by way of a conventional regulator 15. The power may be connected to the electronic circuitry by switch 16. This switch may be operated independently or it may be connected to the switch furnishing the power for the motor ignition. The control means 12, receives information regarding the angular position of the motor from a device 17 and transmits orders in the form of current pulses, to the injectors 7 to 10 by way of the distributor 18, which itself is made dependent on the angular position of the motor by the device 19.

Devices 17 and 18 thus constitute distributing means for synchronizing the time of operation of each of the high speed injectors to a corresponding predetemtined angular position of the crank shaft. The control device 12 delivers current pulses which have a fixed amplitude and a width varying linearly with the manifold pressure, through the distributing means 18 according to a signal furnished by a device 20. The manifold pressure is hereinafter called the fundamental regulatory parameter.

lt should be noted that the particular parameters used for regulation in the embodiment shown are used-purely as illustrative examples andare not intended to be'limiting on the system, since the system is capable of accommodating many other parameters also. a

The current pulses furnished by the device 12 undergo, by way of the devices 21 to 26, corrections based on:

A. The local atmospheric pressuretransmitted by device 21,

I eventually incorporated into device 20.

B. The motor temperature transmitted by device 22.

C. The temperature of the inlet air transmitted by device 23.

D. The speed of depression of the pedal controlling the opening of the butterfly valve, transmitted by device 24. This device plays the role of the acceleration pump in a conventional system having a carburetor.

E. The value of the coefficient of the rate of introduction of air to the motor, a value which depends on the speed of the motor and on the shape of the manifold. This correction is transmitted by the device 25.

F. The angular lead or lag of the injection which is transmitted by the device 26.

A more detailed description of the operation of the overall system is found in U.S. Pat. No. 3,456,628.

Turning now to FIG. 2 it is apparent that the control means 12, a bistable flip-flop, is constituted by an n-p-n transistor T705 and'a p-n-p transistor T710. The collector of T705 is fed by a supply of voltage V through the resistances 707 and 706, while its emitter is grounded. The second transistor T 710 is connected through its emitter with the supply of voltage V,,, while its collector is connected wi h the base of the transistor T705 through the resistances 714a and 715, further resistances 854 and 714 being provided for grounding respectively the base of the transistor T705 and the point connecting said resistances 714a and 715.

The base of the transistor T710 is connected with the connecting point between the resistances 706 and 707, said lastmentioned point fonns also the point E adapted to feed the negative pulse triggering the bistable flip-flop. The collector of the transistor T710 is connected with a condenser 806 through the diode 856 and the resistance 802. The uni-junction transistor T805 is grounded through its base No. 1 while its base No. 2 is fed by a supply V with a voltage which varies with the operative parameters as described in U.S. Pat. No.

3,456,628. The emitter of said uni-junction transistor T805 is connected through the resistances 802a and 802b with the point connecting the condenser 806 with its loading resistance 802. Furthermore a transistor T855 is provided, the collector of which is connected with the point joining the resistances 714,714a and 715 through the diode 857 while its emitter is connected with the emitter of the uni-junction transistor T805, and its is connected with the point connecting the resistances 802a and 802b.

The operation of the above-described circuit is as follows:

When a negative pulse is applied to the point E, the p-n-p transistor T710 becomes conductive and consequently a positive voltage is applied on the base of n-p-n transistor T705 so that it becomes conductive as well. Thus the voltage at the point E and consequently on the base of the transistor T710 is held at a value lower than that of the supply voltage V and thereby the transistor T710 remains conductive as does the transistor T705. At the moment when transistor T710 becomes conductive, the point S on its collector is practically at the voltage V so that the condenser 806 is charged through the diode 856 and the resistance 802. The diode 856 prevents the time required for charging the condenser 806 from varying with the frequency of operation of the arrangement by preventing the complete discharge of said condenser 806 through the resistances 802, 714a, 714 between injection intervals. The condenser 806 therefore remains charged at a very low voltage corresponding to the voltage drop in the transistor T855 and the uni-junction transistor T805 after each end of injection signal. Said diode 856 may be replaced by a constant current diode or the like means such as transistors operating as generators under constant current conditions.

The emitter of the uni-junction transistor T805 is always subjected to the same voltage as the condenser 806 by reason of the connection provided by the resistances 802a, 802b but at the moment at which said voltage is equal to the voltage V applied to the base No. 2 of the single junction transistor T805, with proportionality factor n, said uni-junction transistor T805 becomes suddenly conductive and causes the condenser 806 to be discharged. By reason of the presence of the resistance 802b the voltage on the base of the transistor T855 is higher than that prevailing on its emitter so that said transistor becomes conductive. This produces a speedy discharge of the condenser 806 through the base emitter circuit of said transistor, but furthermore the connecting point between the three resistances 714,714a and 715 is returned practically to the same voltage as that prevailing on the emitter of the transistor T855, that is to a very small voltage, so that the transistor T705 is cut off and the flip-flop returns to its OFF condition.

The arrangement according to the present invention operates with values of the voltage V ranging between zero and the voltage of the supply V It is therefore an easy matter to act on the voltage V with a view to modifying the duration of injection between zero and infinity without any difficulty while an intense negative pulse is obtained for the return of the flip-flop provided a potentiometric voltage-divider is connected in the circuit discharging for condenser 806 in a manner such that the voltage applied to the emitter of the unijunction transistor T805 may be V,; n V

What I claim is:

1. In an electronic system for controlling the duration of fuel injection in an internal combustion engine of the type including a bistable flip-flop, for starting a fuel injection period when switched from a first stable state to a second stable state in response to a pulse depending on a parameter associated with the operation of the engine and for terminating the fuel injection period when switched back to said first stable state, and delay means, for determining the duration of the injection period, including a uni-junction transistor provided with two bases and an emitter, one base of the uni-junction transistor being connected to a common point and the second base of said uni-junction transistor being supplied with a voltage defined by an operative parameter of e engine; a condenser having one terminal connected to the emitter of the uni-junction transistor, and the other terminal connected to said common point; a first resistance connected between the flip-flop and the one temtinal of said condenser; and a voltage source for charging the condenser when the flip-flop is switched to the second state, the improvement comprising:

at least one additional resistance connecting said one condenser terminal with the emitter of said uni-junction transistor and a further transistor, including a base, a collector and an emitter, for switching the bistable flip-flop back to the first state when the voltage of the charged condenser is sufiicient to cause the uni-junction transistor to conduct, the emitter of said further transistor being connected to the emitter of said uni-junction transistor, the collector of said further transistor being connected to the flip-flop, and the base of said further transistor being connected to said one condenser terminal, whereby said further transistor is forward biased into conduction upon discharge of said condenser through said additional resistance to ensure return of said flip-flop to its first stable state for any value of voltage applied to the second base of said uni-junction transistor from zero to the value of said voltage source.

2. The system claimed in claim 1 including means connected between the flip-flop and said first resistance and adapted to prevent modifications in the duration of the in jeetion period resulting from modifications in the frequency of the injector operation.

3. The system claimed in claim 1 including a diode connected between said flip-flop and said first resistance and adapted to prevent modifications in the duration of the injection resulting from modifications in the frequency of injector operation.

4. The system claimed in claim 1 including a diode adapted to operate under constant current conditions connected between said flip-flop and said first resistance and adapted to prevent modifications in the duration of the injection period resulting from modifications in the frequency of injector operation. 

1. In an electronic system for controlling the duration of fuel injection in an internal combustion engine of the type including a bistable flip-flop, for starting a fuel injection period when switched from a first stable state to a second stable state in response to a pulse depending on a parameter associated with the operation of the engine and for terminating the fuel injection period when switched back to said first stable state, and delay means, for determining the duration of the injection period, including a uni-junction transistor provided with two bases and an emitter, one base of the uni-junction transistor being connected to a common point and the second base of said unijunction transistor being supplied with a voltage defined by an operative parameter of the engine; a condenser having one terminal connected to the emitter of the uni-junction transistor, and the other terminal connected to said common point; a first resistance connected between the flip-flop and the one terminal of said condenser; and a voltage source for charging the condenser when the flip-flop is switched to the second state, the improvement comprising: at least one additional resistance connecting said one condenser terminal with the emitter of said uni-junction transistor and a further transistor, including a base, a collector and an emitter, for switching the bistable flip-flop back to the first state when the voltage of the charged condenser is sufficient to cause the uni-junction transistor to conduct, the emitter of said further transistor being connected to the emitter of said uni-junction transistor, the collector of said further transistor being connected to the flip-flop, and the base of said further transistor being connected to said one condenser terminal, whereby said further transistor is forward biased into conduction upon discharge of said condenser through said additional resistance to ensure return of said flip-flop to its first stable state for any value of voltage applied to the second base of said uni-junction transistor from zero to the value of said voltage source.
 2. The system claimed in claim 1 including means connected between the flip-flop and said first resistance and adapted to prevent modifications in the duration of the injection period resulting from modifications in the frequency of tHe injector operation.
 3. The system claimed in claim 1 including a diode connected between said flip-flop and said first resistance and adapted to prevent modifications in the duration of the injection resulting from modifications in the frequency of injector operation.
 4. The system claimed in claim 1 including a diode adapted to operate under constant current conditions connected between said flip-flop and said first resistance and adapted to prevent modifications in the duration of the injection period resulting from modifications in the frequency of injector operation. 